Although 50 years of research findings have causally linked active and passive smoking to cancer and other diseases, further epidemiologic research on the risks of tobacco smoking is still needed. One specific need is for studies in countries other than the developed, western countries where the majority studies have been conducted to date. Most of the world's smokers live outside of the western countries, primarily in Asia where a majority of males are smokers in many countries. Background disease rats and distributions of lifestyle risk factors are notably distinct in these populations, particularly in comparison with populations of previously studied western males. The majority of women, largely non-smokers, and children in Asian countries are exposed to environmental tobacco smoke (ETS). This small grant application requests support to establish a cohort study of active and passive smoking and risk for cancer and other diseases among persons receiving health insurance coverage through the Korean Medical Insurance Corporation (KMIC). The KMIC provides coverage to civil service workers, teachers, and their dependents in the Republic of Korea (South Korea). The total population insured by the KMIC is substantial, accounting for 11% of the country's 43 million residents in 1990. The insured then included approximately 1.2 million workers and an additional 3.4 dependents. A cohort study will be developed using the database of the KMIC. Risk factor information is collected in biennial medical examinations, which are required for the insured workers and are voluntarily completed by dependents. The data collected in the biennial examinations covering smoking and other lifestyle risk for disease and findings from routine laboratory work are also available. Outcomes are tracked through the hospital record system and also by mortality matches. Family members of the insured can be identified through record linkage using the unique identification number of the insured. In an effort to advance understanding of smoking and cancer and other diseases in Asian countries, as well as among Asian Americans, investigators at the Yonsei University and the Johns Hopkins University School of Hygiene and Public Health plan to collaborate in developing and then using this epidemiologic resource to carry out a major program of research on the risks of active and passive smoking in Korea. The Yonsei University has access to the KMIC cohort and already has shown its potential in several reports on cancer and cardiovascular disease. The Johns Hopkins group adds expertise in cohort studies and smoking. This application requests support to establish a comprehensive database in support of the cohort study and to carry out analyses on active and passive smoker and cancer. During the two years of support requested in this small grant application, data will be abstracted from medical records on key exposure variables from exams carried out in 1992 and 1993, providing lifestyle and laboratory data for cohort expected to number approximately 1.6 million adults. Mortality will be tracked from 1992-2003 and inpatient encounters, coded by diagnosis, will be identified for 1998-2003. To demonstrate the potential of the study, an investigation will be carried out on active and passive smoking and lung cancer risk. We intend to set data collection in place to maintain and extend this cohort. The large size of this cohort and the unusually strong possibility for data linkage makes the KMIC population a unique and cost effective study opportunity. This cohort study would have the potential to generate powerful evidence to describe the risk of smoking in a population with distinct background disease rates and distribution of lifestyle risk factors relative to western populations previously studied.